Method of gasifying water containing coal

ABSTRACT

FOR GASIFYING COAL, IN PARTICULAR, WATER CONTAINING GRANULAR RAW BROWN COAL, THE MATERIAL IS INTRODUCED INTO A REACTION TUBE, THE WALLS OF WHICH ARE EXTERNALLY HEATED. THE REACTION TUBE IS DISPOSED APPROXIMATELY HORIZONTALLY SO THAT NO SPONTANEOUS SLIDING OF THE MATERIAL THEREIN MAY OCCUR; THE CONVEYING THEREOF IS EFFECTED BY MEANS OF WATER VAPOR AND POSSIBLY OTHER GASES GENERATED IN THE REACTION TUBE DURING THE HEAT TREATMENT OF THE MATERIAL.

Sept. 2-5, 1973 w. WENZEL ETA.

METHOD OF GASIFYING WATER CONTAINING COAL Filed April 2, 1971 IN VE N TORS United States Patent 3,761,233 METHOD OF GASIFYINiLWATER CONTAINING Werner Wenzel and Hermann Schenck, Aachen, Germany, assignors to Rheinische Braunkohlenwerke A.G., Cologne, Germany Filed Apr. 2, 1971, Ser. No. 130,622 Int. Cl. B65g 53/04; Clllj 3/00, 3/20 US. Cl. 48202 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to a heat treating apparatus particularly for treating, by indirect contact with a heating medium, continuously or intermittently advanced solid fuel such as water containing granular raw brown coal and is in particular concerned with a method of and a structure for conveying the material through a heat treating chamber formed as an externally heated reaction tube.

In known apparatus of the aforenoted type the reaction tube is either vertical or sharply inclined so that the material advances therein by virtue of gravity. It is a disadvantage of such reaction tube structures that for the selection of their optimal diameter, two incompatible factors have to be reckoned with. In the first place, it is a desideratum that the diameter of the reaction tube through which the material passes be relatively small. It is well known that as the diameter of the externally heated reaction tube exceeds a certain magnitude, the temperature conditions in a given cross section tend to lose their uniformity. It is however essential for an eflicient operation of the gasification or other heat treating process that such uniformity be maintained with economical means. In the second place, to ensure a trouble-free advance of the material by gravity in vertical or strongly inclined reaction tubes, the diameter thereof should be relatively large. If the diameter is below a certain value, the risk of clogging appears.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide a reaction tube of the aforenoted type which is of such a design that the material may be conveyed therein without the risk of clogging even in case of a relatively small tube diameter.

Briefly stated, according to the invention, the reaction tube is disposed in an approximately horizontal position so that no spontaneous, solely gravity-caused sliding movement of the material may take place. The material is conveyed towards the discharge end of the reaction tube by virtue of a carrier fluid such as water vapor escaping from the material in the reaction tube during the heating process.

The invention will be better understood as well as further objects and advantages will become more apparent from the ensuing detailed specification of two exemplary embodiments taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic longitudinal sectional view of a first embodiment of the invention and FIG. 2 is a schematic sectional view of a second embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS Turning now to FIG. 1, there is shown a preferably gastight storage chamber 3 in which there is disposed a rotary shovel 4 moved by a shaft 5 which extends through a gastight bushing 6. The shaft 5 is connected to an external motor means (not shown). Above the storage chamber 3 and in communication therewith, there is disposed a charging bin 7, below which there is arranged a dispensing wheel 8. The charging bin 7 is filled with watercontaining granular raw brown coal 18 which is allowed to flow into the storage chamber 3 at such a rate determined by the rotation of the dispensing wheel 8 that a certain amount 18' of the raw material is continuously maintained in the chamber 3.

From an opening in the storage chamber 3 there extends a horizontally arranged reaction tube 20 surrounded by a heating chamber 19 defined by an outer casing 21. The casing 21 is provided with an inlet 22 and an outlet 23 through which a heating medium may flow. The temperature of the heating medium is so selected that the wall of the reaction tube 20 is heated sufliciently for the necessary heat treatment of the material inside the tube, for example, for obtaining vaporization and gasification.

The horizontal arrangement of the reaction tube as opposed to the vertical or sharply inclined reaction tubes of the prior art consistitues an essential feature of this invention. Material conveying problems seemingly appear to be involved with the use of a horizontal tube since displacement of the material by gravity is eliminated. It would thus appear that some mechanical conveying means are required within the reaction tube for moving the material therethrough. It has been unexpectedly found, however, that the granular mass loosens up to a great extent during the heating process and that the water vapor emitted by the material and rushing towards the discharge end of the reaction tube is capable of serving as a carrier fluid thus effecting transport of the loose material. Such a loosening effect cannot occur in a vertical or sharply inclined reaction tube because of the compression of the material due to its own weight. Furthermore, in vertical or sharply inclined tubes, it is exactly the said compression effect which may cause clogging. The arrangement of the reaction tube according to the invention leads to the result that the diameter of the reaction tube may be rendered sufficiently small to ensure uniform temperature conditions over any cross section of the tube without risking clogging thereof. The reaction tube 20 is joined by a tube portion 24 which merges into a separation chamber 25. In the latter the slag discharged from the reaction tube accumulates. At the upper portion of the separation chamber 25 there is provided a gas outlet 26 including a valve 27 for withdrawing the gases generated in the reaction tube 20. The separation chamber 25 is joined by a downwardly extending discharge tube 28 regulated by sliding gates 29 for releasing the slag in the direction of the arrow 26.

Turning now to FIG. 2, the apparatus shown therein is identical to that depicted in FIG. 1, with the exception that the reaction tube slightly slopes in a downstream direction. It is noted that the components corresponding to those depicted in FIG. 1 are designated with reference numerals increased by 100.

A slight inclination of the reaction tube is advantageous since it aids the transport of the material in the reaction tube. It is noted however, that the maximum inclination of the reaction tube is in each instance so designed (taking into account the carrier fluid speed, the surface of the material and tube walls, etc.) that in no case may a spontaneous sliding motion occur by virtue of gravity alone. Such spontaneous sliding motion is disadvantageous in that it is not controllable and defeats the purpose of eliminating the risk of clogging. Generally, it has been found that the maximum angle of inclination is about 20. It may thus be stated that the inclination of the reaction tube 120 is such that it aids, but does not cause the dis placement of the material.

In conclusion, the inventive results may be obtained by either a horizontal (FIG. 1) or a slightly, downstream inclined (FIG. 2) reaction tube, as long as no spontaneous sliding of the material occurs under any given condition. Both in the specification and in the claims the term approximately horizontal is used to designate in a generic manner the arrangement of either FIG. 1 or FIG. 2.

DESCRIPTION OF THE OPERATION OF THE EMBODIMENTS In the description that follows the reference numerals will be those of FIG. 1 and it is to be understood that the same reference numerals increased by 100 apply to the embodiment shown in FIG. 2.

The water-containing granular raw brown coal 18' is fed into the reaction tube 20 by means of the rotating shovel 4 which periodically dips into the material accumulating at the base of the chamber 3. The material is supplied to chamber 3 from the charging bin 7 through the dispensing wheel 8. As the water-containing raw material 31 advance within the reaction tube, it is first dried by the heat emitted by the hot tube wall, whereby water vapors are released. Since the apparatus is preferably gastight upstream, the only possible route of escape is downstream through the open valve 27. As the drying of the material takes place, the latter substantially loosens and loses weight so that the generated water vapor, as it flows downstream, is able to carry, in an approximately horizontal direction, the dried material as a mass of dry coal 32. Then, in the downstream portion of the reaction tube 20 the coal is gasified and reacted upon by the water vapors. The products of the reaction such as gas 34 and the residue 33-which is mostly coal ash-are introduced through the connecting conduit 24 into the separating chamber 25 from which it is discharged through outlet 38 by the periodic actuation of gates 29.

What is claimed is:

1. In a method of gasifying water-containing granular fuel, the improvement comprising in combination the steps of:

(A) externally heating the walls of an approximately horizontal reaction tube,

(B) introducing said granular fuel into said reaction tube at one end thereof,

(C) conveying said granular fuel in an approximately horizontal direction in said reaction tube towards the outlet end thereof by means of water vapors and gases obtained from said granular fuel during the heating thereof in said reaction tube and (D) gasifying said material during step (C).

2. A method as defined in claim 1, wherein said granular fuel is raw brown coal.

3. In a method of gasifying water-containing granular fuel, the improvement comprising in combination the steps of:

(A) introducing said granular fuel into an approximately horizontal reaction tube at one end thereof,

(B) generating water vapors in said reaction tube by drying said fuel by externally heating said reaction tube,

(C) gasifying the dried fuel in said reaction tube by externally heating said reaction tube for obtaining gases and solid residues as a result of a reaction between water and fuel and (D) conveying the dried coal and the residues in an approximately horizontal direction in said reaction tube towards the other outlet end thereof by (means of said water vapor and said gases.

References Cited UNITED STATES PATENTS 3,180,691 4/1965 Wunsch et a1. 302-66 3,009,795 11/1961 AtWell 48-206 2,445,327 7/1948 Keith 48-210 X JOSEPH SCOVRONEK, Primary Examiner US. Cl. X.R. 

